Recently, in-line sputtering apparatuses have been widely adopted in film deposition processes due to its various advantages, such as high yield, fast speed, good coating quality, lower manufacturing costs, etc. In general, a conventional sputtering apparatus includes at least three chambers: a feeding chamber, a deposition chamber and a discharge chamber. During the sputtering process, a substrate (that is to be deposited) is firstly disposed on a substrate carrier. The substrate carrier along with the substrate is disposed on a transport unit which is able to transport the substrate carrier along with the substrate into each of the chambers or among the chambers. The substrate is deposited with a film in the deposition chamber and is then discharged from the discharge chamber to obtain a deposited substrate (as a product). However, during the sputtering process, collisions between energetic ions and a target inside the deposition chamber creates a large amount of heat, causing the temperature inside the deposition chamber to be relatively high. Moreover, if a shortened deposition time and higher deposition efficiency is desired, the temperature in the deposition chamber would be further increased. This means that the temperature of the substrate carrier and the substrate in the deposition chamber are also increased. If the substrate carrier and the substrate cannot dissipate an adequate amount of heat in time, the high temperature may result in deformation or damage of the product, thereby adversely affecting the quality thereof.
Referring to FIG. 1, Taiwanese Patent No. I392756 discloses a conventional substrate carrier unit 1 for sputtering. The substrate carrier unit 1 includes a thermal conductive transport belt 13, a metal tray 12 that is disposed on the thermal conductive transport belt 13, and a substrate carrier 11 that is disposed on the metal tray 12 and that is for carrying a substrate (that is to be deposited) (not shown). The substrate carrier 11 has a bottom surface, and the metal tray 12 has a supporting surface. The supporting surface of the metal tray 12 defines a plurality of sawtooth projections 121, and the bottom surface of the substrate carrier 11 defines a plurality of grooves 111. When the substrate carrier 11 is disposed on the metal tray 12, the sawtooth projections 121 engage the grooves 111 so that the substrate carrier 11 and the metal tray 12 are thermally contacted with each other through a larger thermal contact area. As such, during the sputtering process, heat accumulated on the substrate, the deposited film on the substrate and the substrate carrier 11 can be conducted to the metal tray 12, and then be further conducted to the thermal conductive transport belt 13 to dissipate the heat. Although the metal tray 12 and the thermal conductive transport belt 13 both have high thermal conductivity to dissipate heat, the heat capacity of the metal tray 12 and the thermal conductive transport belt 13 are often not large enough, thereby limiting the heat dissipation efficiency of the conventional substrate carrier unit 1.